Angular 2 - Communicating Between Components with Observable and Subject

<!DOCTYPE html>
<html>
<head>
    <base href="./" />
    <title>Angular 2 - Communicating Between Components with Observable & Subject</title>
    <meta name="viewport" content="width=device-width, initial-scale=1">

    <!-- bootstrap css -->
    <link href="//netdna.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css" rel="stylesheet" />

    <!-- polyfill(s) for older browsers -->
    <script src="https://unpkg.com/core-js/client/shim.min.js"></script>

    <script src="https://unpkg.com/zone.js@0.6.23?main=browser"></script>
    <script src="https://unpkg.com/reflect-metadata@0.1.3"></script>
    <script src="https://unpkg.com/systemjs@0.19.27/dist/system.src.js"></script>

    <script src="systemjs.config.js"></script>
    <script>
        System.import('app').catch(function (err) { console.error(err); });
    </script>
</head>
<body>
    <app>Loading...</app>
</body>
</html>

/**
 * WEB ANGULAR VERSION
 * (based on systemjs.config.js in angular.io)
 * System configuration for Angular samples
 * Adjust as necessary for your application needs.
 */
(function (global) {
  System.config({
    // DEMO ONLY! REAL CODE SHOULD NOT TRANSPILE IN THE BROWSER
    transpiler: 'ts',
    typescriptOptions: {
      // Complete copy of compiler options in standard tsconfig.json
      "target": "es5",
      "module": "commonjs",
      "moduleResolution": "node",
      "sourceMap": true,
      "emitDecoratorMetadata": true,
      "experimentalDecorators": true,
      "removeComments": false,
      "noImplicitAny": true,
      "suppressImplicitAnyIndexErrors": true,
      "typeRoots": [
        "../../node_modules/@types/"
      ]
    },
    meta: {
      'typescript': {
        "exports": "ts"
      }
    },
    paths: {
      // paths serve as alias
      'npm:': 'https://unpkg.com/'
    },
    // map tells the System loader where to look for things
    map: {
      // our app is within the app folder
      app: 'app',

      // angular bundles
      '@angular/common': 'npm:@angular/common@2.2.1/bundles/common.umd.js',
      '@angular/compiler': 'npm:@angular/compiler@2.2.1/bundles/compiler.umd.js',
      '@angular/core': 'npm:@angular/core@2.2.1/bundles/core.umd.js',
      '@angular/forms': 'npm:@angular/forms@2.2.1/bundles/forms.umd.js',
      '@angular/http': 'npm:@angular/http@2.2.1/bundles/http.umd.js',
      '@angular/http/testing': 'npm:@angular/http@2.2.1/bundles/http-testing.umd.js',
      '@angular/platform-browser': 'npm:@angular/platform-browser@2.2.1/bundles/platform-browser.umd.js',
      '@angular/platform-browser-dynamic': 'npm:@angular/platform-browser-dynamic@2.2.1/bundles/platform-browser-dynamic.umd.js',
      '@angular/router': 'npm:@angular/router@3.2.1/bundles/router.umd.js',

      // other libraries
      'rxjs':                      'npm:rxjs@5.0.0-rc.3',
      'ts':                        'npm:plugin-typescript@4.0.10/lib/plugin.js',
      'typescript':                'npm:typescript@2.0.3/lib/typescript.js'
    },
    // packages tells the System loader how to load when no filename and/or no extension
    packages: {
      app: {
        main: './main.ts',
        defaultExtension: 'ts'
      },
      rxjs: {
        defaultExtension: 'js'
      }
    }
  });

  if (!global.noBootstrap) { bootstrap(); }

  // Bootstrap the `AppModule`(skip the `app/main.ts` that normally does this)
  function bootstrap() {

    // Stub out `app/main.ts` so System.import('app') doesn't fail if called in the index.html
    System.set(System.normalizeSync('app/main.ts'), System.newModule({ }));

    // bootstrap and launch the app (equivalent to standard main.ts)
    Promise.all([
      System.import('@angular/platform-browser-dynamic'),
      System.import('app/app.module')
    ])
    .then(function (imports) {
      var platform = imports[0];
      var app      = imports[1];
      platform.platformBrowserDynamic().bootstrapModule(app.AppModule);
    })
    .catch(function(err){ console.error(err); });
  }

})(this);

import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';

import { AppModule } from './app.module';

platformBrowserDynamic().bootstrapModule(AppModule);

import { Routes, RouterModule } from '@angular/router';

import { HomeComponent } from './home/index';

const appRoutes: Routes = [
    { path: '', component: HomeComponent },

    // otherwise redirect to home
    { path: '**', redirectTo: '' }
];

export const routing = RouterModule.forRoot(appRoutes);

import { Component, OnDestroy } from '@angular/core';
import { Subscription } from 'rxjs/Subscription';

import { MessageService } from './_services/index';

@Component({
    moduleId: module.id,
    selector: 'app',
    templateUrl: 'app.component.html'
})

export class AppComponent implements OnDestroy {
    message: any;
    subscription: Subscription;

    constructor(private messageService: MessageService) {
        // subscribe to home component messages
        this.subscription = this.messageService.getMessage().subscribe(message => { this.message = message; });
    }

    ngOnDestroy() {
        // unsubscribe to ensure no memory leaks
        this.subscription.unsubscribe();
    }
}

<!-- main app container -->
<div class="jumbotron">
    <div class="container">
        <div class="col-sm-8 col-sm-offset-2">
            <div *ngIf="message" class="alert alert-success">{{message.text}}</div>
            <router-outlet></router-outlet>
        </div>
    </div>
</div>

<!-- credits -->
<div class="text-center">
    <p>
        <a href="http://jasonwatmore.com/post/2016/12/01/angular-2-communicating-between-components-with-observable-subject" target="_top">Angular 2 - Communicating Between Components with Observable & Subject</a>
    </p>
    <p>
        <a href="http://jasonwatmore.com" target="_top">JasonWatmore.com</a>
    </p>
</div>

export * from './message.service';

import { Component } from '@angular/core';

import { MessageService } from '../_services/index';

@Component({
    moduleId: module.id,
    templateUrl: 'home.component.html'
})

export class HomeComponent {
    constructor(private messageService: MessageService) {}
    
    sendMessage(): void {
        // send message to subscribers via observable subject
        this.messageService.sendMessage('Message from Home Component to App Component!');
    }

    clearMessage(): void {
        // clear message
        this.messageService.clearMessage();
    }
}

<div class="col-md-6 col-md-offset-3">
    <h1>Home</h1>
    <button (click)="sendMessage()">Send Message</button>
    <button (click)="clearMessage()">Clear Message</button>
</div>

export * from './home.component';

import { NgModule }      from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';

import { AppComponent }  from './app.component';
import { routing }        from './app.routing';

import { MessageService } from './_services/index';
import { HomeComponent } from './home/index';

@NgModule({
    imports: [
        BrowserModule,
        routing
    ],
    declarations: [
        AppComponent,
        HomeComponent
    ],
    providers: [
        MessageService
    ],
    bootstrap: [AppComponent]
})

export class AppModule { }

import { Injectable } from '@angular/core';
import { Observable } from 'rxjs';
import { Subject } from 'rxjs/Subject';

@Injectable()
export class MessageService {
    private subject = new Subject<any>();

    sendMessage(message: string) {
        this.subject.next({ text: message });
    }

    clearMessage() {
        this.subject.next();
    }

    getMessage(): Observable<any> {
        return this.subject.asObservable();
    }
}